First it allows you to charge an external lead
acid battery from the car's electrical bus.

Second it isolates the extra battery from the car so it won't be
discharged by the car electronics, and it won't try to participate in starting
the car.

Third it powers your equipment in the
car using the car electrical system, but switches to external battery power
when the car's battery is stolen, or drops below a predetermined voltage.

Fourth, it prevents the external battery from
being over-discharged, keeping it from being damaged.

Fifth, it prevents
your equipment from running the car's battery down so the car can't be started.
In one configuration it cuts off the car's battery when the voltage gets below
13.1 volts, then switches over to the external battery, in other words it
switches over to the auxiliary battery when the engine is shut off and the
alternator stops.

In another configuration the
crossover voltage is lower, say 12.0 volts. This allows your equipment to run
off the car's battery but cut off while the car's main battery still has enough
power to safely start the engine.

To solve these
problems we invented this automotive uninterruptible power supply control
module, or car battery backup system. The idea is that you can connect the
module to the car's electrical bus and it will charge an external 12 volt lead
acid battery of your choice. Your equipment, which can be a small computer,
telemetry equipment, or a car alarm, is connected to the module. This equipment
runs off the automobile's electrical bus until the voltage of the bus drops
below a preset voltage, the "N" voltage (from 13.1 to 11.9 volts, depending on
your needs). Then the external battery takes over. When the external battery
drops below the "P" preset voltage (Between 10 volts and 3 volts depending on
your requirements) the power is cut off to either prevent damage to the
external battery or to run your equipment as long as possible.

Detailed Specifications

PST-DCUPS-3A

Max Charge Current

60-120 milliamps see graph
below

Charging can occur with input
voltages

10V to 15V (this range can be
adjusted during manufacture, usually we set it to come on at 13V input, and to
stop charging when the main battery drops to 12.4V. This allows charging when
the car's engine is turned off.)

The PST-DC-UPS-1212 can be ordered with a range of "N"
and "P" values, as explained in the following table.

Suffixes*

Voltage at which car battery is cut of
from the load

Voltage at which auxiliary battery is cut
off from the load

Why?

N13.1 (most common
choice)

13.1 ±0.2 volts

Load is disconnected from the car electrical bus when the
ignition is switched off

N11.8

11.8 ±0.1 volts

Allows the load to be powered by the car battery most of
the time but still start the car.

P10 (most common choice)

10 volts

When deep cycling of the auxiliary battery is desired.

Other values

Can be programmed to a wide range of custom values

**(For example PST-DCUPS-3A-N13.1-P10 would be a module
which disconnects from the car battery when the car voltage falls lower than
13.1 volts and turns the auxiliary battery off when it falls to 10
volts.)

2. Q: When the module turns off because
both batteries are below their set points when does the module turn back on.
A: The module turns back on only when the car's voltage is restored to the
proper charge voltage. A new auxiliary battery won't turn the module back
on.

Reviews:

The PowerStream UPS was a chance, lucky find.
In spite of my electrical knowledge shortcomings, the system adapted
beautifully to my Brammo Empulse R electric bike, - Im sure the only such
application to any Brammo model bike. The system does everything as advertised
and despite my misgivings about the UPS controller, the final version with
adjusted set-points works perfectly even to charging the backup battery. I now
have a continuous uninterrupted power source required by my Scorpio
motorcycle alarm system and I managed to fit everything into probably the
tightest of available spare space of any bike, electric or ICE. Thanks to you
and crew for the patience and knowledge that made this project happen, and
happy holidays to you all. --RB in Port St. Lucie, FL